Underground mining is a common way of extracting minerals such as coal. In this type of mining considerable amounts of unproductive paid time are expended in transporting mine workers from the surface facilities of the mine to the underground coal face. Travel to and from the coal face in traditional wheeled vehicles is both slow and uncomfortable as the underground roadways traversed are often very rough and at times slope steeply. The underground roadways may consist of clay, sharp shale or crushed ore. They are frequently extremely wet or muddy, and may have a substantial cross-grade.
It will be appreciated in these circumstances that the transportation of mine workers to the coal face in wheeled personnel vehicles is not only slow, it may also result in injuries, such as back injuries, to the workers. The Workers Compensation costs associated with such injuries are large, as is the cost of unproductive time when the mine workers are in transit to the coal face.
Furthermore, the enclosed nature of an underground mine means that hazards and/or discomfort are experienced when toxic and/or noxious gases are emitted by machinery operating in the mine. As diesel engines produce noxious and toxic gases and underground personnel vehicles are conventionally configured with a rearward facing entry positioned just above or behind an exhaust outlet from a diesel engine, a hazard can arise where the exhaust gases are not immediately dispersed. Also, a vehicle travelling over a loose surface produces a good deal of dust which is sucked into the rear of the vehicle. Thus, in an underground mine it is possible that engine exhaust gases and airborne dust will build up in the vicinity of the rearward facing entry and possibly enter the cabin. While this generally is only inconvenient for the personnel in the cabin (as the exhaust gases are noxious and dust is irritating), if toxic gases are carried into the cabin in high enough concentrations a health hazard may exist.
A common configuration for a track in a tracked vehicle is one in which the track is driven by a sprocket. Typically a sprocket will be located at the front and/or rear of the track inside the track and a plurality of road wheels will be located within the loop of the track. The road wheels are typically mounted on trailing road wheel arms which are in turn mounted on torsion bars which pass laterally through the vehicle to provide independent suspension for each of the road wheels.
It is desirable for a tracked vehicle working in an underground mine to have a relatively low ground clearance so as to minimise the height of the vehicle. This allows the vehicle to operate in areas where the roof is low. However, where very rough surfaces are traversed a greater ground clearance is desirable to ensure that large objects on the ground pass underneath the vehicle.